Aquatic and Land Animal Diversity

Animals in General

What is the meaning of the phrase “ontogeny recapitulates phylogeny”?

Ontogeny is how an organism develops from fertilized egg to adult; phylogeny is the evolutionary history of a group of organisms. The phrase “ontogeny recapitulates phylogeny” originated with German biologist and naturalist Ernst Haeckel (1834–1919), and it means that as an embryo of an advanced organism grows, it will pass through stages that look very much like the adult phase of less advanced organisms. Although further research demonstrated that early stage embryos are not representative of our evolutionary ancestors, Haeckel’s general concept does reveal some clues about evolutionary history. In particular, animals with recent common ancestors tend to share more similarities during development than those that do not. For example, a dog embryo and a pig embryo will look more alike through most stages of development than a dog embryo and a salamander embryo.